Climbers Face Lasting Effects if Brain Swells

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Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Extreme mountaineers who develop serious brain swelling at altitude appear to have lasting evidence of small hemorrhages in their brains, a study found.

Note that microhemorrhages in those who had high altitude cerebral edema had a characteristic distribution involving predominantly the corpus callosum.

CHICAGO – Extreme mountaineers who develop serious brain swelling at altitude appear to have lasting evidence of small hemorrhages in their brains, researchers said here.

In a single-center MRI study of 36 mountaineers, patients who'd had high altitude cerebral edema (HACE) had microbleeds in their corpus callosum, while those with other forms of altitude sickness largely did not, Michael Knauth, MD, PhD, of the University Medical Center Goettingen in Germany, and colleagues reported during a press briefing at the Radiological Society of North America meeting here.

"Microbleeds were found almost exclusively in the brains of HACE survivors," Knauth said during the briefing.

HACE typically occurs at altitudes above 7,000 feet and is considered the end stage of severe acute mountain sickness, or altitude sickness.

It's long been thought to be a fully reversible condition if the patient survives, but some work suggests that it does leave traces in the brain – particularly, hemosiderin deposits, or remnants of microbleeds.

These can be picked up on a very sensitive form of MRI called susceptibility-weighted imaging, Knauth said. So he and colleagues conducted these scans on 36 mountaineers, some of whom had experienced various illnesses:

10 had HACE

11 had severe acute mountain sickness

8 had high altitude pulmonary edema (HAPE)

7 had been at altitudes above 7,000 feet but had no altitude sickness

Radiologists interpreting the scans were blinded to the climber's status, and classified each as positive, negative, or questionable for microbleeds.

Overall, Knauth and colleagues found that the microbleeds in the corpus callosum occurred almost exclusively in climbers who'd had HACE -- 8 of the 10 of these mountaineers had definite evidence of microbleeds, while two had "questionable" bleeds.

Only one patient with severe acute mountain sickness also showed evidence of microbleeds, the lone false-positive result, Knauth said.

There was one questionable finding in a patient who'd had HAPE and two questionable findings in those who'd been at altitude without becoming ill.

Knauth said the HACE patients who had been most severely affected showed the most prominent evidence of microbleeds, and he cautioned that the findings don't appear to be a function of altitude as much as severity.

"It's not like you can say that at 8,000 [feet] they'll have so many [microbleeds] and at Everest they'll have double," Knauth said. "But those who have the most severe HACE – the ones that almost died -- have the most severe changes on MRI as well."

He also warned that there don't appear to be many clinical effects of the microbleeds at this point in time – though longer-term effects may be a different story.

"The neuropsychological consequences are unclear, but at the present there are no data to support the hypothesis that they are impaired," he said. "They work normally, but subtle testing of their mental capabilities is still to be performed. But it probably [will show] nothing."

Knauth concluded that the findings counter the idea that HACE is fully reversible, given that this evidence of microbleeds remains for years after the initial injury.

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